"The fact that this problem is complex can no longer be an excuse for doing nothing," Obama says.

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President Barack Obama stands with Vice President Joe Biden as he makes a statement Wednesday in the Brady Press Briefing Room at the White House about policies he will pursue following the massacre at Sandy Hook Elementary School in Newtown.

Updated at 9:46 PM PST on Wednesday, Dec 19, 2012

President Barack Obama on Wednesday asked an administration team to offer "concrete proposals" on curbing gun violence no later than January, in an urgent effort to build on the growing political consensus over gun restrictions following last week's massacre of children at a Connecticut school.

"This time, the words need to lead to action," Obama said. He said he will push legislation "without delay," urged Congress to hold votes on the bill next year, and called for a “wave of Americans” to stand up and say "'enough' on behalf of our kids.”

PHOTOS: Newtown School Shooting

"The fact that this problem is complex can no longer be an excuse for doing nothing," Obama said. "The fact that we can't prevent every act of violence doesn't mean we can't steadily reduce the violence."

President Obama's Second Term

The gunman in Friday's shooting wielded a semi-automatic rifle to kill 20 young children and six adults at the school, after killing his mother at home. He then killed himself.

Obama, who pushed little on gun control during his first term, pressed Congress to reinstate an assault weapons ban, which expired in 2004. He also called for stricter background checks for people who seek to purchase weapons and limited high-capacity clips.

Vice President Joe Biden, a longtime gun control advocate with decades of experience in the Senate, will lead a team that will include members of Obama's administration and outside groups.

"This is not some Washington commission. This is not something where folks are going to be studying the issue for six months and publishing a report that gets read and then pushed aside," Obama said. "This is a team that has a very specific task to pull together real reforms right now."

Biden—along with Attorney General Eric Holder, Education Secretary Arne Duncan, Homeland Security Secretary Janet Napolitano and Health and Human Services Secretary Kathleen Sebelius—will meet with law enforcement leaders from across the country Thursday to begin discussing a path forward, a White House Official told NBC News.

The administration will have to make its gun control push in the middle of tense negotiations with Congress to avoid the "fiscal cliff" of billions of dollars in tax increases and deep spending cuts that will kick in at the end of the year without a deal.

Notably, the first question asked of Obama during a press conference after his gun announcement was about the fiscal talks.

In the days since the shooting, Obama has vowed to use "whatever power this office holds" to safeguard the nation's children after Friday's shooting. Funerals for the victims continued Wednesday, along with the wake for the school's beloved principal.

The shooting has prompted several congressional gun-rights supporters to consider new legislation to control firearms, and there are concerns in the administration and elsewhere that their willingness to engage could fade as the shock and sorrow over the shooting eases.

The most powerful supporter of gun owners and the gun industry, the National Rifle Association, broke its silence Tuesday, four days after the shooting. In a statement, it pledged "to help to make sure this never happens again" and has scheduled a news conference for Friday.

With the NRA promising "meaningful contributions" and Obama vowing "meaningful action," the challenge in Washington is to turn words into action. Ideas so far have ranged from banning people from buying more than one gun a month to arming teachers.

The challenge will be striking the right balance with protecting the 2nd Amendment right to bear arms. Firearms are in a third or more of U.S. households, and suspicion runs deep of an overbearing government whenever it proposes expanding federal authority.

Many pro-gun lawmakers also have called for a greater focus on mental health issues and the impact of violent entertainment like video games. Obama also prefers a holistic approach, with aides saying stricter gun laws alone are not the answer.

Obama said Wednesday that the U.S. needs to make access to mental health care “at least as easy as access to a gun.”

Still, much of the immediate focus is on gun control, an issue that has been dormant in Washington for years despite several mass shootings.

The policy process Obama was announcing Wednesday was expected to include input from the departments of Justice, Education, and Health and Human Services. The heads of those agencies met with Obama at the White House on Monday. The Department of Homeland Security is also expected to play a key role.

Pressure for change has come from several sources this week.

As shares in publicly traded gun manufacturers dropped, the largest firearms maker in the United States said Tuesday it was being put up for sale by its owner, private equity group Cerberus Capital Management, which called the shooting a "watershed event" in the debate over gun control. Freedom Group International makes Bushmaster rifles, the weapons thought to have been used in Friday's killings.

In California, proposed legislation would increase the restrictions on purchasing ammunition by requiring buyers to get a permit, undergo a background check and pay a fee.

The U.S. Conference of Mayors wrote Obama and Congress calling for "stronger gun laws, a reversal of the culture of violence in this country, a commission to examine violence in the nation, and more adequate funding for the mental health system."

The mayors asked for a ban on assault weapons and other high-capacity magazines, like those reportedly used in the school shooting; a stronger national background check system for gun purchasers; and stronger penalties for straw purchases of guns, in which legal buyers acquire weapons for other people.

Formerly pro-gun Democratic Senate Majority Leader Harry Reid has said "a thoughtful debate about how to change laws" is coming soon. Republican Sen. Charles Grassley has said the debate must include guns and mental health. And NRA member Sen. Joe Manchin, a conservative Democrat, said it's time to begin an honest discussion about gun control and said he wasn't afraid of the political consequences.

The comments are significant. Grassley is senior Republican on the Senate Judiciary Committee, which probably would take the first action on any gun control legislation. Reid sets the Senate schedule.